TW202137533A - Image sensor and sensing method thereof - Google Patents

Abstract

The invention relates to an image sensor. The image sensor includes a substrate, a unit pixel, a first polarizer, a second polarizer, and readout circuit. First, incident light is emitted to the unit pixel, and the first polarizer converts incident light into first incident light, and the second polarizer converts incident light into second incident light. Then, The photoelectric conversion element of the unit pixel covered by the first polarizer generates first electrons after receiving the first incident light, and the photoelectric conversion element of the unit pixel covered by the second polarizer generates second electrons after receiving the second incident light. Afterwards, the readout circuit subtracts and integrates the first electron and the second electron to generate a voltage signal corresponding to the number of electrons in the actual signal. Finally, repeat the above steps. Thereby, the image sensor of the present invention effectively increases the full well capacity of the equivalent unit pixel, so as to improve the signal-to-noise ratio of the image sensor of the present invention.

Description

Image sensor and its sensing method

The present invention relates to an image sensor, and particularly relates to an image sensor applied to fingerprint sensing and an image sensing method thereof.

In recent years, thanks to the rapid development and drive of the market in related technical fields such as assisted driving, face recognition, virtual and augmented reality, the market scale of Complementary Metal-Oxide Semiconductor (CMOS) image sensors It is constantly expanding, and in terms of applications currently on the market, smart phones are still the largest terminal application market for CMOS image sensors.

However, with people’s demand for thinner and lighter smartphones, as well as the maturity of CMOS image sensor design and process technology, the volume of components that can be occupied by CMOS image sensors in smartphones is decreasing. For small-sized CMOS image sensors, the conventional shallow trench and ion implantation electrical isolation are restricted by the process technology, which reduces the component volume of the CMOS image sensor, resulting in a decrease in the fill factor of the CMOS image sensor At the same time, the full well capacity of the CMOS image sensor is reduced. In view of this, how to make the CMOS image sensor have a better signal-to-noise ratio is one of the problems that developers should solve.

In addition, when the CMOS image sensor is used in an optical fingerprint recognition environment, the fingerprint image is a pattern composed of many curved lines. The correctness of the fingerprint feature of the fingerprint image will affect the accuracy of the entire device. However, the CMOS image When the sensor receives the fingerprint image, the background light occupies an excessive percentage of the full well capacity compared to the actual signal. As a result, it will affect the identification of fingerprint features in the fingerprint image, thereby affecting the accuracy of optical fingerprint recognition.

Therefore, after observing the above-mentioned deficiencies, the inventor of the present case came up with the present invention.

The object of the present invention is to provide an image sensor, which can generate a first voltage by the number of electrons generated by the photodiode covered by the first polarizer and the second polarizer, respectively, through the calculation of the readout circuit Signal and the second voltage signal, and the first voltage signal and the second voltage signal are subtracted to eliminate the background noise. The full well capacity of the unit pixel enables the image sensor according to the present invention to have a better signal-to-noise ratio.

To achieve the above objective, the present invention provides an image sensor, which includes: a substrate; a plurality of unit pixels are arranged on the substrate, each of the unit pixels includes a photoelectric conversion element, the photoelectric conversion element The conversion element generates electrons after receiving the incident light; a plurality of first polarizers are arranged on a part of the unit pixels, and each of the first polarizers covers a part of each of the unit pixels, The first polarizers are used to change the incident light into a first incident light with a first polarization direction, and the photoelectric conversion element generates a plurality of first electrons after receiving the first incident light; and a plurality of second polarizers , Which is arranged on the other part of the unit pixels, each of the second polarizers covers the other part of each of the unit pixels, and the second polarizers are used to make the incident light Becomes a second incident light with a second polarization direction, the photoelectric conversion element generates a plurality of second electrons after receiving the second incident light; and a plurality of readout circuits, which are coupled to the unit pixels, the After the readout circuit performs subtraction and integration operations on the first electron and the second electron, the readout circuit generates a voltage signal; wherein the incident light includes an actual signal and a background noise, and the readout circuit generates The voltage signal corresponds to the number of electrons in the actual signal.

Preferably, the image sensor according to the present invention is applied in the environment of optical fingerprint recognition.

Preferably, according to the image sensor of the present invention, the photoelectric conversion element is a pinned photo diode (PPD).

Preferably, according to the image sensor of the present invention, the unit pixels further include: a charge transfer element coupled to the photoelectric conversion element, and the charge transfer element transfers electrons to the read A circuit; and a charge reset element, which is coupled to the charge transfer element, the charge reset element is used to reset the electrons stored in the photoelectric conversion element.

Preferably, according to the image sensor of the present invention, the unit pixels further include a source follower, which is coupled to the charge transfer element and the charge reset element, the A source follower is used to reduce the effect of parasitic capacitance.

Preferably, according to the image sensor of the present invention, the polarization direction of the incident light corresponding to the actual signal is the same as the first polarization direction, but the present invention is not limited to this.

Preferably, according to the image sensor of the present invention, the angle between the polarization direction of the incident light corresponding to the actual signal and the first polarization direction is less than 45 degrees, but the present invention is not limited to this.

Preferably, according to the image sensor of the present invention, the actual signal is not much larger than the background noise. Preferably, according to the image sensor of the present invention, the first polarizer and the second polarizer are made of one of a birefringent material and a metal grating, but the present invention is not limited to this.

Preferably, in the image sensor according to the present invention, the first polarization direction and the second polarization direction are orthogonal to each other, but the present invention is not limited to this.

Preferably, according to the image sensor of the present invention, the first incident light includes a first background light, a first background noise corresponds to the number of electrons generated by the first background light, and a second The incident light includes a second background light, the second background noise corresponds to the amount of electrons generated by the second background light, the first background noise is the same as or similar to the second background noise, and the first background The polarization directions of the light and the second background light are different, but the present invention is not limited to this.

Preferably, according to the image sensor of the present invention, the readout circuit is a differential integrator.

In addition, in order to achieve the above-mentioned object, the present invention further provides a display device based on the above-mentioned image sensor, including: a display panel having a display area; and the above-mentioned image sensor disposed on the display panel, wherein , The image sensor correspondingly overlaps the display area.

Preferably, according to the display device of the present invention, the display panel is a liquid crystal display panel, an organic electroluminescence display panel, an organic light emitting diode display panel, or a micro light emitting diode display panel, but the present invention is not limited to this.

In addition, in order to achieve the above-mentioned object, the present invention is based on the above-mentioned image sensor, and further provides a sensing method for eliminating background noise, which includes: a polarization step, an incident light is emitted to an image A sensor, a plurality of first polarizers convert the incident light into a first incident light, and a plurality of second polarizers convert the incident light into a second incident light; a conversion step, the first polarizers are covered The photoelectric conversion element of the unit pixels receives the first incident light to generate a first electron, and the photoelectric conversion element of the unit pixels covered by the second polarizers receives the first electron After two incident light, a second electron is generated; a elimination step, after a readout circuit performs subtraction and integration operations on the first electron and the second electron, the readout circuit generates a voltage signal corresponding to the number of electrons And repeat the above-mentioned polarization step, conversion step, and elimination step N times, where N is one of 0 and a positive integer to produce a better signal-to-noise ratio (SNR, Signal-to-noise ratio) .

Preferably, the sensing method according to the present invention is applied in the environment of optical fingerprint recognition.

Preferably, according to the sensing method of the present invention, the photoelectric conversion element is a pinned photo diode (PPD).

Preferably, according to the sensing method of the present invention, the sensing method further includes the following steps: a reset step, by means of a charge reset element coupled to the charge transfer element, the charge reset element Resetting the electrons stored in the photoelectric conversion element; and a transfer step in which a charge transfer element coupled to the photoelectric conversion element transfers the electrons to the readout circuit.

Preferably, according to the sensing method of the present invention, the unit pixels further include a source follower, which is coupled to the charge transfer element and the charge reset element, and the source A source follower is used to reduce the effect of parasitic capacitance.

Preferably, according to the sensing method of the present invention, the polarization direction of the incident light corresponding to the actual signal is the same as the first polarization direction.

Preferably, according to the sensing method of the present invention, the angle between the polarization direction of the incident light corresponding to the actual signal and the first polarization direction is less than 45 degrees.

Preferably, according to the sensing method of the present invention, the actual signal is not much larger than the background noise.

Preferably, according to the sensing method of the present invention, the first polarizer and the second polarizer are made of one of a birefringent material and a metal grating, but the present invention is not limited to this.

Preferably, according to the sensing method of the present invention, the first polarization direction and the second polarization direction are orthogonal to each other, but the present invention is not limited to this.

Preferably, according to the sensing method of the present invention, the first incident light includes a first background light, a first background noise corresponds to the number of electrons generated by the first background light, and the second incident light The light includes a second background light, a second background noise corresponds to the amount of electrons generated by the second background light, the first background noise is the same as or similar to the second background noise, and the first background light It is different from the polarization direction of the second background light, but the present invention is not limited to this.

Preferably, according to the sensing method of the present invention, the readout circuit is a differential integrator.

In summary, the image sensor and its sensing method provided by the present invention mainly use the image sensor of the present invention in conjunction with a sensing method that eliminates background noise, thereby increasing the full well capacity of the equivalent unit pixel, so that The image sensor according to the present invention can accommodate more effective electrons, thereby improving the signal-to-noise ratio of the image sensor of the present invention.

In order to enable those skilled in the art to understand the purpose, features, and effects of the present invention, the following specific embodiments and accompanying drawings are used to explain the present invention in detail as follows.

The inventive concept will now be explained more fully hereinafter with reference to the accompanying drawings in which an exemplary embodiment of the inventive concept is shown. The advantages and features of the concept of the present invention and the method of achieving the same will be apparent by the exemplary embodiments described in more detail with reference to the accompanying drawings. However, it should be noted that the inventive concept is not limited to the following exemplary embodiments, but can be implemented in various forms. Therefore, the exemplary embodiments are provided only for exposing the concept of the present invention and allowing those skilled in the art to understand the category of the concept of the present invention. In the drawings, the exemplary embodiments of the inventive concept are not limited to the specific examples provided herein and are exaggerated for clarity.

The terms used herein are only used to illustrate specific embodiments, and are not intended to limit the present invention. Unless the context clearly indicates otherwise, the terms "a" and "the" in the singular form used herein are intended to also include the plural form. The term "and/or" as used herein includes any and all combinations of one or more of the related listed items. It should be understood that when an element is referred to as being “connected” or “coupled” to another element, the element may be directly connected or coupled to the other element or intervening elements may be present.

Similarly, it should be understood that when an element (such as a layer, region, or substrate) is referred to as being "on" another element, the element can be directly on the other element, or intervening elements may be present. In contrast, the term "directly" means that there are no intermediate components. It should be understood that when the terms "include" and "include" are used in this text, it means that the stated features, integers, steps, operations, elements, and/or components exist, but do not exclude one or more other features , Integers, steps, operations, elements, components, and/or the existence or addition of groups thereof.

In addition, the exemplary embodiment in the detailed description will be explained by a cross-sectional view which is an idealized exemplary diagram of the concept of the present invention. Accordingly, the shape of the exemplary figure can be modified according to manufacturing technology and/or allowable errors. Therefore, the exemplary embodiments of the inventive concept are not limited to the specific shapes shown in the exemplary figures, but may include other shapes that can be produced according to the manufacturing process. The regions illustrated in the drawings have general characteristics and are used to illustrate the specific shape of the element. Therefore, this should not be regarded as being limited to the scope of the inventive concept.

It should also be understood that although the terms "first", "second", "third", etc. may be used in this specification to describe various elements, these elements should not be limited to these terms. These terms are only used to distinguish each element. Therefore, the first element in some embodiments may be referred to as the second element in other embodiments, and this does not deviate from the teachings of the present invention. The exemplary embodiments of aspects of the inventive concept illustrated and described herein include their complementary counterparts. Throughout this specification, the same reference number or the same indicator represents the same element.

In addition, the exemplary embodiments are described herein with reference to cross-sectional views and/or plan views, where the cross-sectional views and/or plan views are idealized exemplary explanatory diagrams. Therefore, it is expected that there will be a deviation from the illustrated shape due to, for example, manufacturing technology and/or tolerances. Therefore, the exemplary embodiments should not be viewed as being limited to the shapes of the regions shown herein, but are intended to include shape deviations caused by, for example, manufacturing. Therefore, the regions shown in the figures are schematic, and their shapes are not intended to illustrate the actual shape of the regions of the device, nor to limit the scope of the exemplary embodiments.

Fig. 1 is a schematic diagram of an image sensor according to the present invention. As shown in FIG. 1, the image sensor 100 according to the present invention includes: a substrate 11, a unit pixel 12, a first polarizing plate 13, a second polarizing plate 14, and a readout circuit 15.

Specifically, the image sensor 100 according to the present invention can be applied to fingerprint recognition and face recognition. In addition, the image sensor 100 according to the present invention can be a back-illuminated CMOS image sensor or Front-illuminated CMOS image sensor, but the invention is not limited to this.

Specifically, please refer to FIG. 1, the unit pixels 12 are disposed on the substrate 11, and each of the unit pixels 12 includes at least one photoelectric conversion element 121. Wherein, the photoelectric conversion element 121 receives incident light R to generate electrons, and the photoelectric conversion element 121 also has the ability to accumulate the above-mentioned electrons, but the present invention is not limited to this.

Specifically, the photoelectric conversion element 121 may be an element that generates and accumulates electrons corresponding to incident light R. For example, the photoelectric conversion element 121 may be selected from one of a photodiode, a photo transistor, a photo gate, a pinned photo diode (PPD), or a combination thereof. It should be further explained that the charge storage capacity of the photoelectric conversion element 121 has its limit, which causes the unit pixel 12 to have a full well capacity (FWC) limit.

Specifically, the unit pixel 12 may have a structure with one transistor. In some embodiments, the unit pixel 12 may have a structure with three transistors. For example, the unit pixel 12 may form a 3T-APS (3 transistor-Active Pixel Sensor) structure, and other suitable transistor structures may also be used. For example, in some embodiments, the unit pixel 12 may have a structure with four transistors, such as a 4T-APS (4 transistor-Active Pixel Sensor) structure. However, the present invention is not limited to this

Specifically, please refer to FIG. 1, the first polarizer 13 is disposed on a part of the unit pixels, and each of the plurality of first polarizers 13 covers a part of the unit pixels 12. The first polarizer 13 is used to make the incident light R become the first incident light R ₁ with a first polarization direction (not shown), and the photoelectric conversion element 121 generates the _{first incident light R 1 after receiving the first incident light R 1} First Electronics (not shown).

Specifically, please refer to FIG. 1, the second polarizer 14 is disposed on another part of the unit pixels, and each of the plurality of second polarizers 14 covers another of the unit pixels 12 In part, the second polarizer is used to make the incident light R into the second incident light R ₂ having a second polarization direction (not shown), and after the photoelectric conversion element 121 receives the second incident light R ₂ Generate a second electron (not shown).

Specifically, in some preferred embodiments of the present invention, the first polarization direction and the second polarization direction are orthogonal to each other, and the first polarizer 13 and the second polarizer 14 may be made of birefringent materials. It is made with one of the metal gratings, but the present invention is not limited to this.

Specifically, the readout circuit 15 is coupled to the unit pixels 12. After the readout circuit 15 performs subtraction and integration operations on the first electron and the second electron, the readout circuit 15 generates Voltage signal of the number of electrons (not shown).

Please refer to FIG. 2. FIG. 2 is a schematic diagram illustrating the full well capacity of the unit pixel according to the present invention. As shown in FIG. 2, L ₁ represents the limit of the full well capacity (FWC) of the _{photoelectric conversion element 121, and L 2} represents that the photoelectric conversion element 121 receives the first incident light R _{1 having the first polarization direction.} The number of first electrons generated later (not shown). The first incident light R ₁ includes the actual signal R _s and the background light R _B , and the actual signal R _s has a certain degree of polarization. The polarization direction of the actual signal Rs is the same or the included angle is the polarization direction of the first polarizer Less than 45 degrees, and the background light R _B is unbiased polarization. Specifically, L ₂ contains an electronic number L _B R _s actual signals generated by background light and electron number R _B Ls generated, wherein, Ls represents the number of the photoelectric conversion element 121 generates an electronic signal corresponding to the actual R _s is. And L _B of the photoelectric conversion element 121 represents the number of electrons generate electron dark current contribution of background light corresponding to the R _B. At this time, when the actual signal is not much larger than the background light R _s R _B, it will make the unit 12 pixel full well capacity due to the background light easily R _B is saturated, resulting in the image sensor can not achieve a better signal to noise ratio.

It is worth mentioning that, in this implementation, the referred fingerprint recognition application means that the fingerprint signal is not much larger than the background, but the present invention is not limited to this.

In view of this, the image sensor 100 according to the present invention covers a part of the unit pixels 12 by the first polarizer 13 and covers another part of the unit pixels 12 by the second polarizer 14 to respectively Integrate the accumulated and stored electrons in a unit time, where the first electrons stored in a part of the unit pixels 12 covered by the first polarizer 13 are integrated into the first electron quantity (not shown). The electrons stored in the unit pixels 12 in the other part covered by the second polarizer 14 are integrated into the second electron quantity (not shown).

It should be further explained that the first incident light R ₁ includes a first background light (not shown), and the second incident light R ₂ includes a second background light (not shown), wherein the number of first electrons includes The first background noise (not shown) caused by the first background light, and the second electron quantity includes the second background noise (not shown) caused by the second background light, wherein the first background noise It is the same or similar to the second background noise, and the polarization directions of the first background light and the second background light are different, so the readout circuit 15 can subtract the first electron quantity and the second electron quantity. operation, to eliminate the background light and dark current number R _B unit pixels 12 of the electronic storage and accumulation caused by the readout circuit 15 generates a voltage signal corresponding to the actual signals R _s, does not contain background noise.

It is worth mentioning that in under-display optical fingerprint recognition applications, the background noise eliminated according to the present invention may include moire patterns and OLED panel patterns, but the present invention is not limited thereto.

Please refer to FIG. 3, which is a flowchart illustrating the steps of the sensing method of the present invention. As shown in FIG. 3, the present invention further provides a sensing method, which can be applied to the above-mentioned image sensor 100, and the sensing method includes the following steps:

Polarization Step S _1, the R emission incident to the image sensor 100, a first polarizing plate 13 converts the incident light is first incident R R _1, the second polarizing plate 14 converts the incident light R is incident on a second Light R ₂ , and then perform the conversion step S ₂ .

Converting step S _2, the unit pixel by the first polarizing film 13 covers the photoelectric conversion element 121 12 is provided for receiving a first incident light to generate a first electron R _1, the second polarizing film 14 by such covered The photoelectric conversion element 121 of the unit pixel 12 _{generates second electrons after receiving the second incident light R 2} , and then performs the elimination step S ₃ .

After eliminating the step S _3, the first electronic readout 15 and performs subtraction of the second electronic circuit and an integration operation, which corresponds to the number of electrons 15 generates a voltage signal.

Finally, repeat the above steps, the method and principle are the same as those described above, and the description will not be repeated here. It is worth mentioning that by repeating the above steps, the actual signal R _s can be continuously integrated but the background noise is not integrated. In addition, the sensing method of the present invention can also perform the polarization step S ₁ , the conversion step S ₂ , and the elimination step S ₃ only once, but the present invention is not limited to this.

Whereby, in accordance with the present invention, the image sensor 100 is based on, and with the sensing method provided by the present invention, which system can successfully eliminate the dark current of the electron and the ambient background light energy generated R _B generated, The effect of effectively increasing the full well capacity of the unit pixel 12 without changing the size of the full well capacity is achieved, so that the image sensor 100 according to the present invention can accommodate more effective electrons, thereby enhancing the image perception of the present invention. The signal-to-noise ratio of the detector 100.

(First embodiment) Hereinafter, the first embodiment of the image sensor 100 of the present invention will be described with reference to the drawings.

Please refer to FIG. 4, which is a system diagram of the image sensor according to the first embodiment of the present invention. As shown in FIG. 4, the image sensor 100 according to the first embodiment of the present invention is applied to a fingerprint sensing system. The image sensor 100 includes: a substrate 11, a unit pixel 12, a first polarizer 13, The second polarizer 14 and the readout circuit 15.

Specifically, please refer to FIG. 5, which is a schematic diagram illustrating the position of the image sensor according to the first embodiment of the present invention. As shown in FIG. 5, the first polarizer 13 is disposed on a part of the unit pixels. Each of the first polarizers covers at least one of the unit pixels. When the fingerprint image 200 is generated When there are a plurality of incident lights R, the first polarizer is used to change the incident lights R into the first incident light R ₁ with a first polarization direction (not shown). It should be further explained that, in this embodiment, the first polarization direction is set as the polarization direction of the fingerprint image 200, but the present invention is not limited to this.

Specifically, as shown in FIG. 4, the second polarizer 14 is disposed on another part of the unit pixels, and each of the second polarizers covers at least one of the unit pixels. When the fingerprint When the image 200 generates a plurality of incident lights R, the second polarizer is used to turn the incident lights R into second incident lights R ₂ with a second polarization direction (not shown).

It should be further explained that, in this embodiment, the first polarizing direction and the second polarizing direction are orthogonal to each other, but the user can choose the first polarizing direction and the second polarizing direction arbitrarily according to the requirements of the system used. Polarization direction, but the present invention is not limited to this.

It should be further explained that, in this embodiment, the first polarizing direction and the second polarizing direction can also be left-handed and right-handed polarizing directions orthogonal to each other, but the present invention is not limited to this.

Specifically, please refer to FIG. 6, which is a schematic diagram illustrating the structure of the image sensor according to the first embodiment of the present invention. In this embodiment, the unit pixel 12 further includes a charge transfer element 122 and a charge reset element 123. Among them, the charge transfer element 122 is coupled to the photoelectric conversion element 121, and the charge transfer element 122 transfers electrons to the readout circuit 15; the charge reset element 123 is coupled to the charge transfer element 122, and the charge is regenerated The setting element 123 is used to reset the charge stored in the photoelectric conversion element 121.

……..公式(1)

……..公式(2)

……..公式(3)It should be further explained that the effective electron calculation method accumulated by the image sensor 100 according to the present invention is shown in the following formula, referring to formula (1), pixel_1 represents the photoelectricity of the unit pixel 12 covered by the first polarizer 13 receiving a first electronic conversion element 121 by R ₁ generated after the first incident light, 100% SIG lines represent the polarization direction since the first fingerprint image with the same direction of polarization 200, so the first polarizing plate 13 covers the unit pixels the photoelectric conversion element 121 may be 12 percent of the fingerprint image to produce an electronic, 50% BGL line 200 represents background light due to the R _B may have an arbitrary polarization direction, so the first polarizing film photovoltaic unit pixel 13 covers 12 The conversion element 121 only generates 50% _{of the electrons of the background light R B} ; referring to formula (2), pixel_2 indicates that the photoelectric conversion element 121 of the unit pixel 12 covered by the second polarizer 14 receives the second incident light R ₂ The second electron generated later, 0% SIG means that the first polarization direction is consistent with the polarization direction of the fingerprint image 200, and the first polarization direction and the second polarization direction are orthogonal to each other, so the second polarizer the unit pixels 14 of the photoelectric conversion elements covered 12 121 does not receive any fingerprint image based 200,50% BGL denotes background light due to the R _B may have an arbitrary polarization direction, the second polarizing film 14 covered by the unit pixel 121 of the photoelectric conversion element 12 may be another portion of the background light fifty percent of the R electron _B; see equation (3), it is understood that a read-out circuit according to the present invention may be formula (1) By calculating with formula (2), the user can obtain 100% of the electrons generated by the fingerprint image 200, but the present invention is not limited to this.

……..Formula 1)

…….. Formula (2)

…….. Formula (3)

Please refer to FIG. 7, which is a schematic circuit block diagram of the image sensor according to the first embodiment of the present invention. As shown in FIG. 7, the circuit ϕ ₁ and circuit ϕ _1d inside the readout circuit 15 are formed by the first charge generated by the photoelectric conversion element 121 of the unit pixel 12 covered by the first polarizer 13 and the second polarizer 14 covered by the second charge unit pixels 12 of the photoelectric conversion element 121 respectively store the generated readout circuit 15 to the interior of the capacitor C _S, [Phi] the internal circuit of the readout circuit _152, based circuit φ _2d and the first charge The second charge is transferred to the capacitor C _f , so that the readout circuit 15 performs a subtraction operation. The control timing of the circuit ϕ _{1d is the delay of the circuit ϕ 1} control timing, the control timing of the circuit ϕ _2d is the delay of the circuit ϕ ₂ control timing, and the circuit ϕ _{op_rst} within the readout circuit 15 is used to reset the readout circuit 15 Operational amplifier. Accordingly, the readout circuit 15 may generate a voltage signal corresponding to a real signal, and the success of eliminating the dark current of the electron energy environment background light generated R _B generated. In addition, by repeating the above operations, the voltage signal can be continuously integrated. Equivalently, the real signal is integrated, so as to increase the full well capacity of the equivalent unit pixel 12 without changing the size of the full well capacity. Efficacy, but the present invention is not limited to this.

Please refer to FIG. 8. FIG. 8 is a flowchart illustrating the steps of performing the sensing method according to the first embodiment of the present invention. As shown in FIG. 8, the present invention further provides a sensing method, which can be applied to the above-mentioned image sensor 100, and the image sensing method includes the following steps:

In the reset step S ₁ ′, the charge reset element 123 coupled to the charge transfer element 122 resets the electrons stored in the photoelectric conversion element 121, and then the polarization step S ₂ ′ is performed.

In the polarization step S ₂ ′, the incident light R is emitted to the image sensor 100, the first polarizer 13 converts the incident light R into the first incident light R ₁ , and the second polarizer 14 converts the incident light R into the second Incident light R ₂ , and then perform the conversion step S ₃ ′.

In the conversion step S ₃ ′, the photoelectric conversion element 121 of the unit pixel 12 covered by the first polarizer 13 _{generates first electrons after receiving the first incident light R 1} , and the photoelectric conversion element 121 of the unit pixel 12 is covered by the second polarizer 14 The photoelectric conversion element 121 of the covered unit pixel 12 _{generates second electrons after receiving the second incident light R 2} , and then performs the transfer step S ₄ ′.

Transfer step S ₄ ', coupled by the photoelectric conversion element 121 is transferred optoelectronic elements 122, 122 Electron Transfer optoelectronic element is transferred to the readout circuit 15, is then performed to eliminate the step S _5'.

Elimination step S ₅ ', the readout circuit 15 after the first and second electronic subtraction and performs electronic integral operation, the read circuit 15 generates a voltage corresponding to the number of electronic signals.

Finally, repeat the above steps, the method and principle are the same as those described above, and the description will not be repeated here.

For example, please refer to FIG. 9 in conjunction with FIG. 4 to FIG. 8. FIG. 9 is a timing diagram illustrating the sensing method of the image sensor according to the first embodiment of the present invention. As shown in FIG. 9, first, incident light R is emitted to the image sensor 100, and the charge transfer element 122, the charge reset element 123, and the circuit ϕ _{op_rst are} activated to reset the photoelectric conversion element 121 and the readout circuit 15; Next, the photoelectric conversion element 121 in the unit pixel 12 receives the incident light R to generate electrons. The photoelectric conversion element 121 of the unit pixel 12 covered by the first polarizers 13 receives the first incident light R1. generating a first, a second polarizing film by these unit pixels 14 of the photoelectric conversion element 121 covered by 12, receives the second incident light to generate a second electronic after ₂ R; then coupled by the photoelectric conversion element 121 The charge transfer element 122 is activated to transfer electrons to the readout circuit 15; at the same time, the circuit ϕ _{op_rst is} activated to reset the electrons stored in the readout circuit 15; after that, the circuit ϕ ₁ and the circuit ϕ _1d are activated in sequence to The first electrons generated by the photoelectric conversion element 121 of the unit pixel 12 covered by the first polarizer 13 and the second electrons generated by the photoelectric conversion element 121 of the unit pixel 12 covered by the second polarizer 14 are respectively transferred to the capacitor C _S ; Then, the circuit ϕ ₂ and the circuit ϕ _2d are activated sequentially to transfer the first electron and the second electron to the capacitor C _f , so that the arithmetic unit 15 performs the subtraction operation; thereby, the circuit ϕ 2 and the circuit ϕ 2d are The image sensor 100 stores 100% of the electrons generated from the fingerprint image 200, but the invention is not limited to this. Finally, the above steps are repeated to perform the integration operation, so that the image sensor 100 according to the present invention repeatedly receives the incident light R, but the present invention is not limited to this.

In this way, based on the image sensor 100 of the first embodiment of the present invention, combined with the sensing method provided by the present invention, it can successfully eliminate _{the electrons generated by the background light R B} and the heat generated by the environment. The dark current electrons achieve the effect of increasing the full well capacity of the equivalent unit pixel 12 without changing the size of the full well capacity, so that the image sensor 100 according to the first embodiment of the present invention can accommodate more Effective electrons can improve the signal-to-noise ratio of the image sensor 100 of the present invention.

Other examples of the image sensor 100 are provided below, so that a person with ordinary knowledge in the technical field of the present invention can more clearly understand the possible changes. The elements indicated by the same reference numerals as in the foregoing embodiment are substantially the same as those described above with reference to FIG. 6. The elements, features, and advantages that are the same as those of the image sensor 100 will not be repeated.

Please refer to FIG. 10, which illustrates the image sensor 100 according to the second embodiment of the present invention. Compared with the first embodiment, the main structural difference of the second embodiment is that in the image sensor 100 of the second embodiment, the unit pixel 12 may have a structure with four transistors, that is, It includes a charge reset device 123 (reset device), a charge transfer device 122 (charge transfer device), a source follower 22 (source follower) and a select gate 23 (select gate). The source follower can reduce the effect of parasitic capacitance. The materials and other characteristics used in the unit pixel 12 according to the second embodiment of the present invention are similar to those of the unit pixel 12 according to the first embodiment of the present invention, and will not be repeated here.

Please refer to FIG. 11, which illustrates the image sensor 100 according to the third embodiment of the present invention. Compared with the second embodiment, the third embodiment differs in the main structure of the third embodiment in that the position of the select gate 23 is different. In the image sensor 100 of the third embodiment, the unit pixel 12 has a structure of four transistors, and its structural principle is similar to the unit pixel 12 according to the second embodiment of the present invention, and according to the third embodiment of the present invention The materials and other characteristics of the unit pixel 12 are similar to those of the unit pixel 12 according to the first embodiment of the present invention, and will not be repeated here.

Please refer to FIG. 12, which illustrates the image sensor 100 according to the fourth embodiment of the present invention. Compared with the third embodiment, the main structural difference of the fourth embodiment is that the image sensor 100 of the fourth embodiment further includes a gain amplifier 21. The gain amplifier 21 receives and amplifies the signal of the unit pixel 12, so that the signal-to-noise ratio can be further improved. The materials and other characteristics used in the unit pixel 12 according to the fourth embodiment of the present invention are similar to those of the unit pixel 12 according to the first embodiment of the present invention, and will not be repeated here.

Please refer to FIG. 13, which illustrates the image sensor 100 according to the fifth embodiment of the present invention. Compared with the fourth embodiment, the fifth embodiment differs in the main structure of the image sensor 100 of the fifth embodiment, in which the gain amplifier 21 is of a differential type, so it is better for The ability to suppress noise from the power supply is better. The materials and other characteristics of the unit pixel 12 according to the fifth embodiment of the present invention are similar to those of the unit pixel 12 according to the first embodiment of the present invention, and will not be repeated here.

It is understandable that those with ordinary knowledge in the technical field of the present invention can make various changes and adjustments based on the above examples, which will not be listed here.

Hereinafter, an embodiment of the image sensor according to the present invention applied to a display device will be described.

Please refer to FIG. 14, which is a schematic diagram of a structure of a display device according to a preferred embodiment of the present invention. The display device 400 includes a display panel 300 and an image sensor 100. The display panel 400 has a display area. The image sensor device 100 is disposed on the display panel 300. The image sensor device 100 correspondingly overlaps the display area. Specifically, the display panel 300 may be, but not limited to, a liquid crystal display panel (LCD), an organic electroluminescence display panel, an organic light emitting diode display panel, or a micro light emitting diode display panel (μLED display).

Finally, the technical features of the present invention and its achievable technical effects are summarized as follows:

Firstly, based on the image sensor 100 of the present invention, combined with the sensing method provided by the present invention, _{the electrons generated by the background light R B} and the dark current electrons generated by the thermal energy in the environment are successfully eliminated to achieve The effect of improving the full well capacity of the equivalent unit pixel 12 without changing the size of the full well capacity.

Second, according to the dark current of an electronic image sensor 100 of the present invention, which system by eliminating the background light R _B generated by the electronics and the environment the heat generated, so that the image sensor 100 can be accommodated according to the present invention More effective electrons can improve the signal-to-noise ratio of the image sensor 100 of the present invention.

Third, to solve the problem that background noise occupies an excessive percentage of the full well capacity _{compared to the actual signal R s . By eliminating the electrons generated by the background light R B} and the dark current electrons generated by the thermal energy in the environment, the cost is improved. The signal-to-noise ratio of the invented image sensor 100 further improves the accuracy of optical fingerprint recognition.

The above is a description of the implementation of the present invention through specific specific examples. Those with ordinary knowledge in the art can easily understand the other advantages and effects of the present invention from the content disclosed in this specification.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the scope of the present invention; all other equivalent changes or modifications made without departing from the spirit of the present invention should be included in the following patent scope Inside.

100: image sensor 11: substrate 12: unit pixel 121: photoelectric conversion element 122: charge transfer element 123: charge reset element 13: first polarizer 14: second polarizer 15: readout circuit 21: gain amplifier 22: source follower 23: selector gate 200: fingerprint image 300: display panel 400: display device L ₁ : line L ₂ : line Ls: line L _B : line R: incident light R ₁ : first incident light R ₂ : Second incident light R _B : Background light R _{s :} Actual signal S ₁ : Polarization step S ₂ : Conversion step S ₃ : Elimination step S ₁ ': Reset step S ₂ ': Polarization step S ₃ ': Conversion step S ₄ ': Transfer step S ₅ ': Elimination step ϕ ₁ : Circuit ϕ ₂ : Circuit ϕ _1d : Circuit ϕ _2d : Circuit ϕ _{op_rst} : Circuit C _S : Capacitance C _f : Capacitance

Figure 1 is a schematic diagram of an image sensor according to the present invention; 2 is a schematic diagram illustrating the full well capacity of a unit pixel according to the present invention; FIG. 3 is a flowchart illustrating the steps of implementing the sensing method of the present invention; 4 is a schematic diagram of the image sensor system according to the first embodiment of the present invention; 5 is a schematic diagram illustrating the position of the image sensor according to the first embodiment of the present invention; 6 is a schematic diagram illustrating the structure of the image sensor according to the first embodiment of the present invention; FIG. 7 is a schematic circuit block diagram of the image sensor according to the first embodiment of the present invention; 8 is a flowchart illustrating the steps of performing the sensing method according to the first embodiment of the present invention; FIG. 9 is a timing diagram illustrating the sensing method of the image sensor according to the first embodiment of the present invention; FIG. 10 illustrates an image sensor according to a second embodiment of the present invention; Figure 11 illustrates an image sensor according to a third embodiment of the present invention; Figure 12 illustrates an image sensor according to a fourth embodiment of the present invention; Figure 13 illustrates an image sensor according to a fifth embodiment of the present invention; FIG. 14 is a schematic diagram of the structure of a display device according to a preferred embodiment of the present invention.

100: Fingerprint recognition system

11: substrate

12: unit pixel

121: photoelectric conversion element

13: The first polarizer

14: second polarizer

15: readout circuit

Claims (26)

An image sensor for receiving an incident light. The image sensor includes: A substrate; A plurality of unit pixels are arranged on the substrate, and each of the unit pixels includes a photoelectric conversion element, and the photoelectric conversion element generates electrons after receiving the incident light; A plurality of first polarizers are arranged on a part of the unit pixels, each of the first polarizers covers a part of each of the unit pixels, and the first polarizers are used to make the The incident light becomes a first incident light with a first polarization direction, and the photoelectric conversion element generates a plurality of first electrons after receiving the first incident light; A plurality of second polarizers are arranged on another part of the unit pixels, each of the second polarizers covers the other part of each of the unit pixels, and the second polarizers are used for Turning the incident lights into a second incident light having a second polarization direction, and the photoelectric conversion element generates a plurality of second electrons after receiving the second incident light; and A plurality of readout circuits, which are coupled to the unit pixels. After the readout circuit performs subtraction and integration operations on the first electrons and the second electrons, the readout circuit generates a voltage signal; Wherein, the incident light includes an actual signal and a background noise, and the voltage signal generated by the readout circuits corresponds to the number of electrons in the actual signal. The image sensor according to claim 1, which is used in the environment of optical fingerprint recognition. The image sensor according to claim 1, wherein the photoelectric conversion element is a pinned photo diode (PPD). The image sensor according to claim 1, wherein the unit pixels further include: A charge transfer element coupled to the photoelectric conversion element, the charge transfer elements transfer electrons to the readout circuit; and A charge reset element is coupled to the charge transfer element, and the charge reset element is used to reset the electrons stored in the photoelectric conversion element. The image sensor according to claim 1, wherein the unit pixels further include a source follower, which is coupled to the charge transfer element and the charge reset element, and the source A source follower is used to reduce the effect of parasitic capacitance. The image sensor according to claim 1, wherein the polarization direction of the incident light corresponding to the actual signal is the same as the first polarization direction. The image sensor according to claim 1, wherein the angle between the polarization direction of the incident light corresponding to the actual signal and the first polarization direction is less than 45 degrees. The image sensor according to claim 1, wherein the actual signal is not much larger than the background noise. The image sensor according to claim 1, wherein the first polarizer and the second polarizer are made of one of a birefringent material and a metal grating. The image sensor according to claim 1, wherein the first polarization direction and the second polarization direction are orthogonal to each other. The image sensor according to claim 1, wherein the first incident light includes a first background light, a first background noise corresponds to the number of electrons generated by the first background light, and a second incident light The light includes a second background light, a second background noise corresponds to the amount of electrons generated by the second background light, the first background noise is the same as or similar to the second background noise, and the first background light It is different from the polarization direction of the second background light. The image sensor according to claim 1, wherein the readout circuit is a differential integrator. A display device includes: A display panel with a display area; and The image sensor according to any one of claims 1 to 12 is arranged on the display panel, wherein the image sensor correspondingly overlaps the display area. The display device according to claim 13, wherein the display panel is a liquid crystal display panel, an organic electroluminescence display panel, an organic light emitting diode display panel, or a micro light emitting diode display panel. A sensing method, which includes the following steps: In a polarization step, an incident light is emitted to an image sensor, a plurality of first polarizers convert the incident light into a first incident light, and a plurality of second polarizers convert the incident light into a second incident light ； In a conversion step, the photoelectric conversion element of the unit pixels covered by the first polarizers generates a first electron after receiving the first incident light, and the unit pixels covered by the second polarizers The photoelectric conversion element generates a second electron after receiving the second incident light; In a elimination step, after a readout circuit performs subtraction and integration operations on the first electron and the second electron, the readout circuit generates a voltage signal corresponding to the number of electrons; and Repeat the above-mentioned polarization step, conversion step, and elimination step N times, where N is one of 0 and a positive integer. The sensing method according to claim 15, which is applied in the environment of optical fingerprint recognition. The sensing method according to claim 15, wherein the photoelectric conversion element is a pinned photo diode (PPD). The sensing method according to claim 15, which further includes the following steps: A reset step, by means of a charge reset element coupled to the charge transfer element, the charge reset element resets the electrons stored in the photoelectric conversion element; and In a transfer step, a charge transfer element coupled to the photoelectric conversion element transfers electrons to the readout circuit by the charge transfer element. The sensing method according to claim 15, wherein the unit pixels further include a source follower, which is coupled to the charge transfer element and the charge reset element, and the source A source follower is used to reduce the effect of parasitic capacitance. The sensing method according to claim 15, wherein the polarization direction of the incident light corresponding to the actual signal is the same as the first polarization direction. The sensing method according to claim 15, wherein the angle between the incident polarization direction and the first polarization direction corresponding to the actual signal is less than 45 degrees. The sensing method according to claim 15, wherein the actual signal is not much larger than the background noise. The sensing method according to claim 15, wherein the first polarizer and the second polarizer are made of one of a birefringent material and a metal grating. The sensing method according to claim 15, wherein the first polarization direction and the second polarization direction are orthogonal to each other. The sensing method according to claim 15, wherein the first incident light includes a first background light, a first background noise corresponds to the number of electrons generated by the first background light, and the second incident light It includes a second background light, a second background noise corresponding to the amount of electrons generated by the second background light, the first background noise and the second background noise are the same or similar, and the first background light and The polarization direction of the second background light is different. The sensing method according to claim 15, wherein the readout circuit is a differential integrator.

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